Purifying dicyclopentadiene



Patented Apr. 2, 1946 2,397,601 I roams DICYCLOPENTADIENE Howard L. Gerhart, Milwaukee, Wis., and Leon M. Adams, Corpus Christi, Tex., assignors to Pittsburgh Plate Glass Company, a corporation of Pennsylvania Serial No. 512,770

No Drawing. Application December 3, 1943,

6 Claims.

The present invention relates to the separation of cyclic diene hydrocarbons of lower molecular weight from crude sources thereof and it has particular relation to the separation of cyclopentadiene and/or dicyclopentadiene from tars and drip oils constituting a cheap but impure source thereof.

One object of the invention is to provide a simple and inexpensive method whereby cyclopentadiene or dicyclopentadiene may be removed in very high yield from the impure sources and without substantial inclusion of contaminants such as coumarone, indene and other impurities associated therewith and yet in form well adapted for use in resin preparation.

- A'second object is to provide a process whereby the dimer of cyclopentadiene is recovered in a form particularly adapted to polymerization under heat and pressure with drying oils to pro-" vide resins useful as plastics or asoils that can be substituted for tung oil or other drying oils.

These and other objects will be apparent from consideration of the following specification and the appended claims.

It has heretofore been proposed to prepare resinous products of addendum polymerization of cyclopentadiene or its dimer, dicyclopentadiene.

By suitableprocedures, a considerable number of avoid cracking of the dicyclopentadiene.- The impure fraction can also be cracked at atmospheric pressure but the yield of cyclopentadiene is never 100%. Some of thedicyclopentadiene that oxidize in air and form insoluble powders.

In a copending application to Howard L. Gerhart, Serial Number 324,392, filed March 16, 1940, and entitled Resinous material, are disclosed methods of forming improved products from cyclopentadiene and dicyclopentadiene. In particular, there are disclosed processes of forming copolymers of cyclopentadiene or dicyclopentadiene with unsaturated glyceride oils or free fatty acids from such oils.-

The usual procedure in' obtaining cyclopentadiene for the manufacture of these copolymers-is to distill coal tar, drip oil (Dripolene) cracked distillates or hydrocarbon mixtures from other sources and to remove the fraction boiling in the range 160 to 180 C. This fraction is further fractionated at reduced pressure to obtain dicyclopentadiene of greater purity. In the case of many mixtures, which contain hydrocarbons having a boiling point close to 170 C. it is very difilcult to obtain dicyclopentadiene in a purity exceeding 80 to 90%. This fractionation must be performed at reduced pressure in order .to

forms a residue in the still pot.

By operating according to the present disclosure all the dicyclopentadiene is made availablein purified form for the copolymerization process. The invention is .based upon the discovery that when a fraction containing dicyclopentadiene is heated to 200 to 230 C(cyclopentadiene polymers of low molecular weight are formed which, are insoluble in the normal diluting. impurities. These polymers are the trimer, tetramer, pentamer, hexamer, etc.', of {cyclopentadiene which appear as a slush, since they dissolve with difflculty in the non-polymerized liquids. From this slush the diluting impurities can be separated by several mechanical means; 7

The present invention involves the further discovery that these polymers of a molecular weight within a range of about 3 to 5 units of cyclopentadiene or CsHa are excellentlyadapted for 00 polymerization with unsaturated glyceride oils and free fatty acids ofsuch oils to provide 'prod ucts which may be solid resins suitable for-us e as gums in other oils or which may, themselves, be drying oils, dependent upon the amount of oil present in the copolymerization reaction and the degree of copolymeriza-tion.

The solid, low molecular weight polymers free from impurities can be used'in place of dicyclopentadiene in the charge to prepare the cyclopentadiene copolymer.

The following examples are illustrative of "the invention:

, Example I One hundred sixty pounds of commercial.

"Dripolene having the boiling range 26 to 200 C. was fractionated into 12 fractions in a column. To illustrate the difiiculty of obtainingpure dicyclopentadiene, three fractions having the boiling ranges (a) 78-84" C./ mm., (1)) 84-90 C./60 mm., (0) 90-95 C./60 mm., were found to contain 50%, 78%, available cyclopentadiene respectively as determined. by carefully cracking at atmospheric pressure. In each case there was a still pot residue which contained some dicyclopentadiene polymers or reaction products for instance, of dicyclopentadiene with indene.

Example II The fractions can be used in quantitative amounts according to the present disclosure in the preparation of cyclopentadiene type resins.

I tetramer It was filter pressed to remove the liquid com ponents. The liquid filtrate was cooled tofreeze out" more polymeric material which was then filtered preferably at low temperatures.

Example 11b The slush was agitated with an equal volume of acetone which is a precipitant for most of the polymers and a solvent for the impurities. This granular precipitate is easy to filter.

Example He The slush was heated at reduced pressure to remove 15% of liquid boiling at 30 to 125 at 7 mm. pressure. The residue in the flask was a waxy solid.

A charge consisting of 320 parts of residue from method 3 and 480 parts linseed oil was heated for 5 hours at 270 C. in an autoclave.

Thinned in naphtha to 50% solids the'copolymer The reaction product was thinned with petroleum naphtha. It dries as well or better than a Chinawood oil varnishg'has excellent water resistance. and is well suited for the preparation of varnishes and enamels by the well-known methods.

The advantage in using the relatively purified trimer and tetramer is that the color of the copolymer is lighter. The glyceride oil copolymers so prepared are equal in every respect to copolymers prepared from dicyclopentadiene and it is intended that methods and products described in copending applications using dicyclopentadiene shall be equivalent when the trimer-tetramerpentamer mixture is used in place of the dimer.

It is possible that some cyclopentadiene may reactwith the olefinic diluting impurities under the conditions by which the slush is formed. If such reaction products accumulate in the solid phase of the slush and are charged with oil to prepare the copolymer no harm will result. In fact, many such secondary reaction products are useful in the preparation of these copolymers as described in copending application Serial No.

The charge can be varied over wide limits. The copolymer which is most useful as a varnish type product will contain from to 70% oil and 70 to 30% polycyclopentadiene. Copolymers which contain less than 30% oil are inclined to be brittle and are of the nature of varnish type gums. Copolymers which contain greater than has an E body (Gardner-Holdt scale) and is.

useful as an enamel or varnish vehicle for air" drying and baking applications There appears to be no qualitative difference between the comethod of separation above. The separated slush can be substituted for dicyclopentadlenein any of the methods previously disclosed for the preparation of thermal type copolymers.

At reduced pressure, some of the products in the slush may be distilled and identified although this is not a required procedure for the operation of this invention. Thus, the slush from Example 11 was distilled at reduced pressure as described in Example IIc; Further distillation at a more diminished pressure produced fractions boiling at 110-210 C. at 10 mm. mercury pressure.- From these fractions pure trimer and were crystallized and identified.

Example III A copolymer was prepared from the relatively purified trimer-tetramer mixture having the distillation range 97 C. to 190. C,.at'4 mm. pressure. 320 parts of this solid and 480 parts alkali refined linseed oil was charged into an autoclave provided with agitator; pressure gage and sampling valve. The autoclave was heated according to the following schedule:

polymers prepared from the products of either 70% oil are very flexible and tend to be of the nature of synthetic oils. A useful copolymer as prepared from linseed oil, 10% dicyclopentadiene by this process dries rapidly and may be considered to be a synthetic substitute for Chinawood oil for many applications.

The following compositions are illustrative of the charges which can be used:

Example A Parts Unbodied alkali refined linseed oil 600 Lower polymer of cyclopentadiene '400 Ea'ample B Parts Unbodied alkali refined soya oil 540 Lower polymer of cyclopentadiene 450 Example 0 Parts Alkali refined medium bodied linseed oil 500 Lower polymer of cyclopentadiene 500 Example D Parts Alkali refined unbodied linseed oil 600 Trimer or tetramer of cyclopentadiene 400 EzampleE Parts Alkali refined unbodied soya oil 900 Lower polymer of cyclopentadiene The copolymer from this composition is a synthetic oil which dries as rapidly as alkali refined Lower polymer of cyclopentadieneu nu- 1,000

In the examples, "lower polymers or cyclopentadiene" are those containing from 3 to 8 cyclic CsI-Ia units.

The forms of the invention herein disclosed are to be considered merely as exemplary. Numerous modifications may be made therein without departure from the spirit of the invention or the scope of the appended claims.

We claim:

1. A method of preparing a resinous product which comprises, in the absence of catalysts, heating in a closed system a mixture of (A) polymers o1 cyclopentadiene from a class consisting of its trimer, tetramer, and pentamer and (B) an unsaturated glyceride oil to a temperature above 160 C. until a. copolymer soluble in petroleum naphtha is obtained.

2. A process as defined in claim 1 in which the slyceride oil is linseed oil.

4. A method of preparing a resinous product A which comprises heating in a closed system "a mixture of trimer, tetramer, and pentamer of cyclopentadiene dissolved in an unsaturated glyceride oil and in the absence of polymerization catalysts to a temperature within a range of 160 to 280 C. until a. copolymer soluble in petroleum naphtha is obtained.

5. A process as defined in claim 4 in which the unsaturated glyceride oil is linseed oil.

6. A process as defined in claim 4 in which the glyceride oil is linseed oil and is within a range of 30 to 90% based upon the oil cyclopentadiene polymer mixture.

HOWARD L. GERHART. LEON M. ADAMS. 

